Technical Abstract:
Fumonisins are mycotoxins produced by several Fusarium species, especially Fusarium proliferatum and Fusarium verticillioides, which are common pathogens of maize worldwide. Consumption of fumonisins has been shown to cause a number of mycotoxicoses, including leucoencephalomalacia in horses, pulmonary edema in swine, and liver cancer and neural tube defects in experimental rodents. Consumption of fumonisin-contaminated maize also has been associated epidemiologically with human esophageal cancer in some areas of the world where maize is a dietary staple. Although F. proliferatum is a major cause of maize ear rot, this species also is a minor component of the wheat head blight complex worldwide and has been associated with incidents of black point disease of wheat kernels in the U.S.A. The major aim of the present study was to characterize nine F. proliferatum strains from wheat from Nepal for ability to cause wheat kernel black point under greenhouse conditions, and for fumonisin contamination of infected kernels. For comparative purposes, the study also included three Fusarium strains isolated from U.S. maize: two F. proliferatum strains and one F. verticillioides strain. Fungal strains were applied by spray or injection of macroconidia to spikes of five wheat cultivars (two soft white spring wheats, one hard red spring wheat, and two durum wheats). All strains produced kernel discoloration and black point, and most strains had some effect on kernel weight and germination. Most strains also produced fumonisins in kernels, but at relatively low levels of less than 10 ug/g (combined fumonisin B1, B2 and B3) as determined by liquid chromatography-mass spectroscopy. However, one strain from Nepal produced high levels of more than 100 ug/g of fumonisins in kernels. These preliminary data indicate a potential for fumonisin contamination of wheat infected with F. proliferatum. Surveys are underway to determine the natural occurrence of F. proliferatum and fumonisins in U.S. wheat with black-point disease. Those interested in contributing black-point wheat samples for fumonisin analysis are encouraged to contact the corresponding author.